It is generally known in the art of internal combustion engine design to use fuel rails to deliver fuel to individual fuel injectors. A fuel rail is essentially an elongated tubular fuel manifold connected at an inlet end to a fuel supply system and having a plurality of ports for mating in any of various arrangements with a plurality of fuel injectors to be supplied. Typically, a fuel rail assembly includes a plurality of fuel injector sockets in communication with the fuel rail, the injectors being inserted into the sockets and held in place in an engine head by bolts securing the fuel rail assembly to the head. Fuel rail assemblies are typically used on internal combustion engines with multi-point fuel injection systems.
Gasoline fuel injection arrangements may be divided generally into multi-port fuel injection (MPFI), wherein fuel is injected into a runner of an air intake manifold ahead of a cylinder intake valve, and direct injection (DIG), wherein fuel is injected directly into an engine cylinder, typically during or at the end of the compression stroke of the piston. Diesel fuel injection (DID) is also a direct injection type.
For purposes of clarity and brevity, wherever DIG is used herein it should be taken to mean both DIG and DID, and fuel rails in accordance with the invention as described below are useful in both DIG and DID engines.
DIG fuel rails assemblies require high precision in the placement of the fuel rail relative to the fuel line that delivers pressurized fuel from a fuel tank to the fuel rail because the spacing and orientation of the sockets along the fuel rail assembly must exactly match the three-dimensional spacing and orientation of the fuel injectors as installed in cylinder ports in the engine. A stiff fuel line to fuel rail connection may create undesired stresses in the fuel rail assembly when assembled in an engine head.
Furthermore, a DIG fuel rail assembly must sustain much higher fuel pressures than MPFI fuel rail assemblies to assure proper injection of fuel into a cylinder having a compressed charge. For example, DIG fuel rails may be pressurized to 100 atmospheres or more, whereas MPFI fuel rails must sustain pressures of only about 4 atmospheres. Accordingly, a tight seal is needed, for example, at the fuel line to fuel rail connection.
Efforts to provide a sealed fuel rail to fuel line connection included, for example, a spherical fuel rail inlet. Currently, such spherical fuel rail inlet is achieved by machining a sleeve that has one end formed as a ball, by gradually reducing the diameter of a fuel rail inlet, by press fitting the sleeve onto the reduced diameter section of the fuel rail inlet, and by creating a braze joint to ensure attachment of the sleeve to the fuel rail. While the ball of the sleeve enables a sealed connection of the fuel rail to the fuel line, multiple parts and assembly processes are needed to achieve this. Multiple parts and assembly steps create extra cost and cycle time. Also, metal forming and brazing processes can produce significant stresses in the formed or joint parts that are undesirable.
What is needed in the art is a simple and inexpensive sealed connection of a fuel rail to a fuel line.
It is a principal object of the present invention to provide a spherical fluid connection end integral with a fuel rail that is formed by plastic deformation of an inlet end of the fuel rail.